1. Field of the Invention
The invention relates to an image forming apparatus for forming an image.
2. Description of the Related Art
Image forming apparatuses of an electrophotographic type have been developed to a digital hybrid apparatus (MFP: multifunction printer) having a plurality of functions or a full-color MFP for overlaying multi-color toner images and simultaneously transferring them owing to such a digitizing process for directly writing electronic information by a laser beam and forming an image. While small and low-cost home-use printers have been widespread, an apparatus for business use which has advanced functions and can cope with the printing of a high speed and a large quantity is also demanded.
In the image forming apparatuses of the electrophotographic type, as well as toner as a developer, a developing unit for supplying the toner onto the surface of a photosensitive drum and developing an electrostatic latent image is also consumable. Therefore, a structure for taking out the developing unit on the assumption that a periodic exchange and maintenance work are executed is provided.
A taking-out structure of a developing unit also serving as a jam process of sheets has been disclosed in Japanese Patent Application Laid-Open No. H05-080597. In such a structure, a casing structure in which a sheet conveying surface is divided into upper and lower portions and can be opened and closed is used, the developing unit is dropped and arranged into the lower portion of the casing structure, and the developing unit can be pulled out upward by rotating upward and opening the upper portion of the casing structure.
A taking-out structure of a developing unit in which a right side surface of an image forming apparatus is opened and the developing unit is taken out in the upper oblique direction has been disclosed in Japanese Patent Application Laid-Open No. H05-341642.
A developing unit in which a knob is attached to an upper surface of the developing unit and the developing unit can be lifted upward has been disclosed in Japanese Patent Application Laid-Open No. H07-181753.
An image forming apparatus in which a developing unit is arranged under a developer storing portion which can supplement a developer to the developing unit has been disclosed in Japanese Patent Application Laid-Open No. 2003-122192. The developing unit can be taken out to a side surface side of the image forming apparatus through a portion under the developer storing portion.
An image forming apparatus in which a slide rail is arranged to thereby enable a developing unit to be horizontally pulled out has been disclosed in Japanese Patent Application Laid-Open No. H10-078737.
In a copying apparatus or a multifunction printer of the electrophotographic type, an image reading apparatus (so called an image scanner) is arranged in an upper portion of an apparatus main body for forming images. Therefore, the constructions in which the casing structure is divided into the upper and lower portions and the developing unit is taken out upward as shown in Japanese Patent Application Laid-Open Nos. H05-080597 and H07-181753 cannot be used. This is because the divided upper portion becomes very large and heavy due to the image reading apparatus and the like and it is extremely unreasonable in terms of the structure, a setting space, and a working space.
In the case of realizing the high-speed and large-quantity printing by providing the developer storing portion over the developing unit as shown in Japanese Patent Application Laid-Open No. 2003-122192, the construction in which the side surface of the image forming apparatus is opened and the developing unit is taken out in the upper oblique direction as shown in Japanese Patent Application Laid-Open No. H05-341642 cannot be used. This is because the large developer storing portion has been arranged in the upper oblique position of the developing unit.
According to the apparatus which can cope with the high-speed and large-quantity printing as shown in Japanese Patent Application Laid-Open No. 2003-122192, since the developing unit has a developing sleeve and an agitating mechanism, it is large and fairly heavy. It is, therefore, difficult for an ordinary person to move the developing unit in the horizontal direction in a groping state while supporting it by hand.
At present, a sales style in which an option apparatus is provided for the apparatus main body with the common specifications in accordance with circumstances of the individual user is a main stream. This is because if the apparatus main body and various kinds of parts are used in common, both of the cost reduction and the improvement of quality and reliability can be accomplished and it is also advantageous for reduction in amount of stocks and shortage of a deadline for delivery. However, if the option apparatus is attached to the side surface of the apparatus main body, an access to the inside of the apparatus including the pull-out of the developing unit becomes inconvenient.
For example, there is a case where a developer supplementing apparatus (152: FIG. 1) is externally attached to an upper portion of the side surface of the apparatus main body in order to cope with a large-quantity continuous process. In such a case, the developer supplementing apparatus becomes an obstacle when the developing unit is pulled out. It is not easy to bypass the developer supplementing apparatus and pull out the developing unit in the groping state while supporting the heavy weight of the developing unit. Each time the user hits the developing unit to an ambient portion, the toner drops out to the surroundings.
There is also a case where a multi-feeding unit (4: FIG. 1) is arranged to the side surface of the image forming apparatus in order to cope with large long sheets or the like which cannot be enclosed in a cassette built in the image forming apparatus, OHP sheets or the like with little opportunity, hard sheets which cannot be conveyed by an ordinary conveying path, sheets which are easily bent and cannot be conveyed by the ordinary conveying path, and the like.
The multi-feeding unit supplies the sheet to the photosensitive drum through a rectilinear short conveying path without using the sheet cassette arranged in a lower portion of the casing structure. However, in such a case, as shown in Japanese Patent Application Laid-Open Nos. 2003-122192 and H10-078737, it is difficult to horizontally take out the developing unit to the side surface of the image forming apparatus. This is because the multi-feeding unit has been arranged at the side position where the developing unit is to be taken out.